Conventional nitride semiconductor devices include, for example, GaN-based nitride semiconductor devices, which are applied to blue or green light emitting devices (LEDs), high speed switching and high output devices, such as MESFET, HEMT, and the like.
One example of such a typical GaN-based nitride semiconductor light emitting device includes a nitride semiconductor light emitting device 10 having an activation layer 15 of a multi-quantum well structure. Such a typical nitride semiconductor light emitting device 10 includes a sapphire substrate 11, an n-type nitride layer 12, an activation layer 15, and a p-type nitride layer 17. In addition, a transparent electrode layer 18 and a p-side electrode 19b are sequentially formed on an upper surface of the p-type nitride layer 17, and an n-side electrode 19a is formed on an exposed surface of the n-type nitride semiconductor layer 12.
Such a typical GaN-based nitride semiconductor light emitting device emits light through recombination of electrons and holes in the activation layer 15. In order to improve luminous efficacy of the activation layer 15, the amount of n-type dopants in the n-type nitride layer 12 or the amount of p-type dopants in the p-type nitride layer 17 are increased to increase an inflow amount of electrons or holes into the activation layer 15, as disclosed in Korean Patent Laid-open Publication No. 2010-0027410 (Mar. 11, 2010).
However, when the amount of n-type dopants in the n-type nitride layer 12 or the amount of p-type dopants in the p-type nitride layer 17 is increased, the nitride semiconductor device suffers from significant deterioration in luminous efficacy due to uneven current spreading.
Specifically, since an excess of electrons flows from the n-type nitride layer 12 into some areas of the activation layer 15 and holes generated in the p-type nitride layer 17 are not efficiently moved into the activation layer 15, some area of the activation layer 15 has high current density, whereas the other area of the activation layer 15 have low current density.
Therefore, such a typical GaN-based nitride semiconductor light emitting device is required to have improved luminous efficacy through uniform current spreading in the activation layer 15.